In Fourth Generation (4G) cellular communication systems, such as 3GPP LTE-Advanced and IEEE (Institute of Electrical and Electronics Engineers) 802.16j communication systems, it has been proposed to use Relay Nodes (RNs) to improve user throughput at a cell edge and to enhance overall system coverage. A Relay Node (RN) would have a wireless backhaul connection to an eNodeB (evolved Node B) serving the RN and operate at a lower transmission power level, and provide service to a smaller coverage area, than the eNodeB. The RN would exchange data with a user equipment (UE) served by the RN and would, in turn, transfer data to, and receive data intended for the UE from, the serving eNodeB. The eNodeB also would provide wireless service to users equipment (UEs) in the coverage area of the eNode B not under the coverage of RNs associated with, that is, served by, the eNodeB.
The current proposals provide that when an eNodeB receives a data packet intended for a UE that is served by an associated RN, the eNodeB stores the data packet in a buffer and transmits the data packet to the RN. In response to receiving the data packet, the RN conveys an acknowledgement of the data packet to the eNodeB. In response to receiving the acknowledgement, the eNodeB deletes the data packet from the eNodeB's buffer. The RN also stores the data packet in a buffer and transmits the data packet to the UE. In response to receiving an acknowledgement of the data packet from the UE, the RN deletes the data packet from the RN's buffer.
When the UE is being handed off from a serving, or source RN, to a target RN or to a new, target eNodeB, an issue arises as to how to determine, by the target RN or target or source eNodeBs, data packets that have been correctly received by the source RN but have not been correctly received by the UE, for example, data packets that have not been transmitted by the RN to the UE or data packets that have been transmitted to, but not correctly received by, the UE. Therefore, a need exists for a method and apparatus for communicating which data packets have been delivered to a UE prior to being handed-off by a serving, or source, RN.
One of ordinary skill in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of various embodiments of the present invention. Also, common and well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention.